I have a small tract survey of 155 Acres in Sections 7 and 8. It's inside a larger tract of about 3000 Acres. In the late 1980's we did a power line easement cutting through the larger tract. It was about 4 miles long and was tied to the SW corner of Sec 6 for the POB and the terminus point was tied to the S1/4 of Section 17.
Four miles of line with state plane bearings, tied to two sectional corners set in the 1970's. I know the S1/4 of 17 isn't the same monument from the 1980's description since I had to re-monument it a couple of years ago. So I have both monuments located with GPS in my data base. I put them in this job with their lat, long. and start entering the description figuring it would maybe work. Different monuments, state plane bearings from the 1980's, job done with a T2 and distance meter, NAD27 monuments used for the basis of bearings, what could go wrong. I put in the description starting at the SW of 6 finished it at the S1/4 of 17 and it looked kinda close on my screen. I zoomed in and the tie missed my new monument by 0.15'.
I didn't believe it at first, went through the numbers and sure enough it's all good.
Well you just proved that it's better to be lucky than good 😉. Really tho, nice job with the calcs.
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I've got a bit less than 10ppm in ground to grid error; or .2' in 20,000', add to that the differences between NAD27 az using instruments, and NAD83 with GPS and I expected a few feet. 10 seconds in 20,000' is a foot.
It's probably compensating error, if so I'm taking it and not looking any deeper.
How did you get your new monument off ??? 😉